Molecular dynamics simulations of ultralow hysteretic behavior in super-elastic shape memory alloys

Shape memory alloys (SMAs) that exhibit superelasticity with large recoverable strain and small hysteresis are in demand for practical applications, although their synthesis remains a challenge. We introduce metastable engineering to dope conventional SMA solid-solution atoms of relatively high concentration with weak local lattice distortion to realize ultralow hysteretic superelasticity. Large-scale molecular dynamic (MD) simulations of NiTi-based SMAs are performed to demonstrate how the presence of 2 similar to 4 at.% Nb dopants lead to a stress-induced transition from a metastable pretransitional state to a strainglass state. This is facilitated by a macroscopically homogeneous and continuous phase transformation in the course of superelastic loading and unloading. This spinodal decomposition-like phase transformation process endows SMAs with anhysteretic superelasticity that is insensitive to loading direction and grain size (below 15 nm). These findings show promise of achieving ultralow hysteretic superelasticity with large recoverable strain for SMAs.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

Metastable engineering is used to dope conventional shape memory alloys (SMAs) in order to achieve ultralow hysteretic superelasticity. Large-scale molecular dynamic simulations demonstrate the influence of dopants on the phase transformation process of SMAs.